My 1990 240 is slowly leaking coolant down the driver side of the block near the bell housing, just rearward of the PCV separator box.

It only leaks after the car has been driven for maybe 15 miles at least. I haven't been able to get it to leak just sitting idling but maybe I was impatient.

So here's my dilemma; I think the coolant is coming from the heater hose that is connected to the block just under the intake manifold between cylinders 3 and 4. However, I can't see in there without removing the intake manifold and obviously once that is off I won't be able to run the engine to create the leak to verify the source.

Any ideas how I might verify the leak source? It's been leaking slowly for about 1000 miles so there might just be an obvious trail leading right back to the source.

I do not have a pressure tester.

Well it turns out it was the heater hose. I changed them both out today and found the crack where it was leaking.

I only used a flat blade screwdriver to do the task and it took about an hour moving at a very liesurely pace. Was not nearly as hard as it looked.

Thanks for the help!

I just did the heater hoses and heater valve on my 90 740. It had a loping idle and the flame trap hoses were grungy from the previous owner never having cleaned them, so I did the intake manifold gasket and the oil separator box at the same time. You don't have to remove the injector rail, etc., since you only need about 2 inches of clearance to do the gasket and the other items. I couldn't see the crappy aftermarket clamp on the heater hose at the block anyway. Solved my coolant leak, loping idle, and now I know the flame trap/separator system is clean.

Is there anything else in this area that could leak?

I wouldn't think the temp. sensor would be very likely to leak and I can't think of anything else that carries coolant that is in that area.

While the car is running you could try flexing the hoses around a bit and see if that increases the leak.With a 20 yr.old car changing out the hoses for new ones would not be a bad idea and just might solve the leak issue,although it is kind of a PITA you do not have to remove the intake to change the hose.

Don't have to remove the intake?!?!

I'll have to take another look at it tomorrow.

Do what stripping 90 said: run the engine and manipulate the hoses some. Look for loose/ rusted clamps.

It's an easy - if painstaking - job to change w/o removing the manifold.
--
240s: 2 drivers and some parts cars

You don't have to remove the intake.
With a long screwdriver you can reach the
clamps and remove the hoses. I did mine
last month with a little time and a flashlight
to get a closer look.

Good luck,
Joseph in NM

Hi,


The firewall bulkhead fitting that connects the hoses from inside to outside can also fail.


Goatman

If it is leaking from one of the heater hoses it may be at a location where the hose rubs against the oil or transmission fill tubes. You should be able to see a fine stream of fluid squirting out when the engine is at running temperature and cooling system is pressurized.
Dan